With the blooming development of computer technology and Internet, applications of cloud computing are increasingly popularized. The existing network system provides related services of cloud computing by a data center. The data center usually includes a large number of physical machines such as servers. Each physical machine runs multiple virtual machines. In general, one large-scale data center can usually support more than hundred thousands of physical machines and millions of virtual machines. In addition, the data center further includes a large number of switches, such as Ethernet switches, which can form a local area network for transmitting data packets between the physical machines.
Software-Defined Network (SDN) is a mechanism for converting inflexible and closed hardware-based network architecture with distributed control in conventional art into open programmable network architecture with centralized control management. In the SDN network architecture based on OpenFlow protocol, a SDN controller connected to all network devices is configured to update flow control information, including packet forwarding rules (e.g., an output port for forwarding packet or QoS (Quality of Service control) stored in all network devices (e.g., an OpenFlow switch), so as to manage data transmission paths for all connections in the SDN network. In this way, all network devices in the SDN network can process the data packets according to the rules provided by the SDN controller. Because the SDN network controller can control the transmission paths of data packets for all connections in the SDN network, a network throughput can be improved significantly.
A large amount of data traffics often occurs in transmissions within the local area network when the network system becomes increasingly large in the data center. Normally, those traffics belong to different personal or enterprise tenants. In order to satisfy demands on convenience and security of network management and prevent traffics of different tenants from interfering with one another, administrators usually divide the local area network into a plurality of Virtual Local Area Network (VLAN) and assign one virtual local area network identity (VLAN ID) for each local area network. By doing so, switches are able to control the transmission paths of the data packets according to the VLAN ID in the data packet.
However, in the existing network systems, different virtual local area networks are assigned with different VLAN IDs. In other words, one VLAN ID can only be assigned to one virtual local area network in the same network system. Based on the IEEE 802.1Q standard, the length of the VLAN ID is 12 bits, which can mark 4094 different virtual local area networks. Nonetheless, in the network system with a large-scale physical network and a lot of demands on virtual local area networks, demands on more than 4094 virtual local area networks cannot be satisfied under the limitation by the length of the VLAN ID. Therefore, finding a way to break through the limitation caused by the number of the VLAN IDs in order to deploy more virtual local area networks in the network system is one the major issues to be addressed by persons skilled in the art.